Roll out store-bought sugar cookie dough to 1/4-inch thick on parchment paper.
Use a farm truck cookie cutter to cut out the cookies. Remove the dough between the cookies instead of moving the cookie after the shape has been cut.
Transfer the sheet of parchment paper with the cookies onto your baking sheet.
Bake the cookies according to package directions.
Leave the cookies on the parchment paper and transfer them to a rack, allowing the cookies to cool completely before you frost them.
In order to make the icing, combine all of the icing ingredients in a small bowl and beat on low speed until smooth.
Set aside about ⅓ cup of icing in a second bowl; set aside about ⅓ cup of icing in a third bowl, and about ½ cup of icing in a fourth bowl.
Use the larger portion of icing and add 5-ish drops of red food coloring then stir it until the color is the red you want.
With one smaller portion of icing, add 9 drop of black food coloring and stir it until the color is the black you want. Put this black icing in an airtight container and set aside.
Use the other smaller portion of icing, add 4-ish drop of black food coloring and stir it until the color is the grey you want. Put this grey icing in an airtight container and set aside.
With the ½ cup portion of icing, add 9-ish drop of green food coloring and stir it until the color is the green you want. Put this green icing in an airtight container and set aside.
Place the red icing in a decorating bag with your smallest round tip. Pipe an edge line all the way around the outer edge of each cookie where you want the truck body to be and immediately fill it in, covering the truck’s whole body. Allow this layer of icing to dry for 2-3 hours.
With the black icing, pipe an outline of the tire shape on both the inside and outside rings. Immediately fill it in, covering the tire’s whole outer ring. Add one ¼-inch long line of black icing for a door handle.
Use the green icing to pipe the outline of the Christmas tree shape. Immediately fill it in, covering the tree’s whole area. Allow this layer of icing to dry for 2-3 hours.
With the red icing, trace the general shape of the truck door and any other outline areas you’d like to make, including fenders
Use the grey icing to fill in the center of the hole for the tire’s rim; pipe an outline for the truck’s window and immediately fill this in; and pipe an outline for each of the bumpers and immediately fill them in.
With the red icing, add dots of “ornaments” on the Christmas tree, adding one at the top of each tree, then immediately pressing a yellow star sprinkle into this dot of red icing. Allow this layer of icing to dry for 2-3 hours.
Store any leftover cookies in an airtight container in a single layer.